System and method for storing and searching buy and sell information of a marketplace

A method of storing prospective and actual buying and selling information using a computer system, said method comprising:

• accessing a first data structure, said first data structure including a set of nodes, said set of nodes having nodes with parent node and child node references;
• selecting, by a software agent, a subset of said set of nodes including selecting a first node of subset of nodes, said first node having a parent node, said first node being a child node of said parent node, said parent node having a second child node, during said selecting of said subset of nodes, determining whether a selection of said second child node is possible upon selection of said first node and using said determination to allow or disallow the selection of said second child node;
• recording a list of node selections corresponding to said subset of nodes;
• extracting a set of terms corresponding to said list, wherein said set of terms correspond to product/service information;
• a first program for receiving a series of communications, each communication defining a node to be selected;
• said first program for accessing said first data structure and for determining a set of selectable nodes upon receipt of a communication;
• said first program for causing a presentation about said set of selectable nodes;
• storing said first data structure including storing said list of nodes in said first data structure;
• storing said first data structure including using said set of terms as keys to index said first data structure in a data base;
• storing a second data structure including said set of terms.